nanokernel: Add generic stack routines

Adds the following generic stack routines:
	nano_stack_push()
	nano_stack_stack_pop()
	nano_stack_pop_wait()

Those routines are convenience wrappers for invoking the task, fiber and
ISR (if applicable) specific implementations.

Change-Id: I6e7bb2ca69bb2e3d5ed955654390746e76e4ab92
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>
3 files changed